The long range objective of this research proposal is to obtain further insight, in molecular terms, into the process of eukaryotic gene expression in antibody synthesizing cells. The importance of this project stems from the involvement of the immune response in the generation and maintenance of immunity to infectious diseases, as well as its possible role in protection against malignancy. The use of a mouse myeloma cell line (P3K, MOPC 21) offers several distinct advantages for this purpose. 1) The cells grow in suspension culture and are ideal for in vivo labelling experiments. 2) They synthesize and secrete large quantities of myeloma protein of completely defined primary sequence. 3) Cloning and selection procedures have been developed which allow the isolation of variant clones for genetic analysis. 4) Both translation procedures using cell-free systems and chemical methods for sequence analysis can be used as tools for identifying and characterizing the mRNA's coding for the immunoglobulin H- and L-chains. The following types of investigation are proposed: 1) Isolation and characterization of the hnRNA (pre-mRNA) for the immunoglobulin L- and/or H-chains. 2) The determination of the sequence of the ribosome binding site for the immunoglobulin L-chain and/or H-chain mRNA. 3) Studies on the interactions between membranes, polyribosomes and mRNA during translation.